| The saline soil, which is widely distributed in the world, is a special soil, according to the properties of the salt kept in the soil, the saline soil could be classifed as chlorine saline soil, sub-chlorine saline soil, sub-sulphate salty soil, sulphate salty soil and carbonate-saline soil. The property of saline soil changes in the case of water, the strength of saline soil decreases significantly, then the hazards of foundation subgrade thaw and road collapse happen. The temperature changing will create harm effect on building and road because of soil volume expansion, this problem will be more obvious in the cold area. The western of Jilin province is the biggest distribution area of soda saline-alkaline land in our country. This area is semi-arid-sub-humid continental climate, located in the Songnen rift tectonic deposition environment, it's located in the mid-high latitude areas and belongs to seasonally frozen ground, where the migration regularity of the water and salt in the soil is spectial on account of freezing effect, simultaneously, the water frozes in the process of freezing, causing the relative displacement of soil particles, then soil frost heave occurs. Migration of water and salt in the soil is an important reason of salinization aggravation in this area, and the frost heaving will threaten the safety of buildings and roads, currently there is rare domestic research on these issues, so this article put point on the study of salt and water migration and frost heave in western of Jilin Province.On basis of collection of relevant information, soil samples of Sanzhgou area and Da'an area in the west of Jilin province are taken as reasearch object. Three experiments were carried out:the direct method capillary water rising test, the freezing method water migration test and frost heave test, in order to analyze the characteristics of soil water and salt migration and frost heave laws under different conditions expansion, combing the indicators of soil basic properties (including soil particle size composition, mineral composition, soluble salts, surface area and cation exchange capacity, etc.) obtained by conventional laboratory tests. The main results obtained In this paper are as follows:1. The granularity composition of soil samples in the area mainly is silt, followed by clay; the main mineral composition is the primary minerals, such as quartz, feldspar, and plagioclase, there is a little secondary mineral content; the total soluble salt content is more than 0.3%, the components of soluble salt mainly are Na+ and HCO3-, belonging to soda alkaline saline soil. Affected by the seasons, the content of soluble salts of Sanzhigou (summer) soil samples is the highest in 0.3m below the surface, that of the Sanzhigou (spring) soil samples with the Da'an (spring) and Da'an (autumn) is the highest on the surface, the content of Na+ is consistent with the soluble salt content.2. The results of direct method of capillary water rising test show that the capillary zone in soil samples has something to do with the exchangeable Na+ content, diameter of capillary size and specific surface area of soil samples. The content of exchangeable Na+ of 0.2m～0.3m depth of Sanzhigou (summer) soil samples is higher, as a result, the adsorbed water around soil particles is thick and extended to the full porous, there is not adequate channels for capillary water rising, so three months later, the total height of capillary water rising is only about 4cm, after supplementary tests, the 0.5m, lm depth soil samples of Sanzhigou (summer) contain less exchangeable Na+, the adsorbed water around soil particles is thinner and capillary phenomenon was significant,24 hours later the capillary water rising height was 9cm,10cm or so, the capillary water rising height of the soil samples of 0.2m～0.3m,0.5m,0.7m,1.0m depth of Da'an (spring) were respectively 3cm,3cm,4cm,4cm after 24 hours, which was not very obvious, this was because Da'an (spring) soil samples not only contained more exchangeable sodium, but also had larger particles specific surface area, making the water molecules bound and capillary water rising very difficult.3. The results of freezing test showed that both of water migration and salt migration occurred in the freezing process. The upper part of soil samples firstly frozed under the action of negative temperature, after the liquid water in soil frozed, the water in the lower part migrated upward and added at the effect of temperature potential, while at the bottom of the soil samples in the flume, there was a constant head supply, so the water at the upper and lower of soil samples migrated upward, the moisture content increases with height growth, the central moisture content of soil samples increased with height decreases. In addition, the degree of soil compaction greater the smaller the increase in moisture migration. Frozen soil salinity in the migration phenomenon is also evident. The greater the degree of compaction, saltThe greater the migration points.4. During the frost heave test, the soil salt content, water content and compaction respectively had different degree effect on soil frost heave. The results showed that the soil began frost heave when the moisture content of soil samples was up to a certain value, which just is the initial moisture content of frost heave, and that of soil samples with different compaction are different, according to the test results, the initial moisture content of frost heave of soil samples decreased along with the increase of compaction, so the initial moisture content of frost heave of the degree of 85%compaction soil samples were the highest, being 20%～21%, while that of 95%degree was the lowest, being less than 18%. When the water content in soil samples is more than a certain value, the effect of salt content on the frost heave gradually became apparent. The results showed that when the soil moisture content was more than 22%, with the increase in the degree of compaction, water content under the same salt content of soil samples in each group's comparative results from the frost heave rate:1.5%salt content>1.2%salt content>0.5%salt content >0.3%salt content>0.0%salt content, tend to be 0.0%salt content> 1.5%salt content> 1.2%salt content> 0.5 salt content> 0.3%salt content, basically showed that the rate of frost heave growed with the increase of salt content in the soil samples.
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